Sparkingchip:
So f we install foundation earthing for an installation with a lower Ra than the DNO network earthing what happens to the touch voltages in the installation, if anything?
In normal circumstances, not a lot. During conventional L-PE faults, not too much either (the effect is still small compared with the normal metallic return path). In a broken CNE event on a PME system you'd still have 230V nominal between two different points each connected to true earth (possibly more than 230V on a 3-phase system in some peculiar circumstances) - just how that 230V (or whatever) divides between the DNO's and customer's systems will differ - the lower Ra the less the customer sees and the more the DNO's system (including N/CNE) will be affected.
To be honest I can't see it being worse than the original PME system for a CNE break near the substation where the DNO's electrode was a few tens of metres of copper buried within the substation compound while the consumers side was connected to literally miles of metallic gas and water pipes.
- Andy.
Sparkingchip:
So f we install foundation earthing for an installation with a lower Ra than the DNO network earthing what happens to the touch voltages in the installation, if anything?
In normal circumstances, not a lot. During conventional L-PE faults, not too much either (the effect is still small compared with the normal metallic return path). In a broken CNE event on a PME system you'd still have 230V nominal between two different points each connected to true earth (possibly more than 230V on a 3-phase system in some peculiar circumstances) - just how that 230V (or whatever) divides between the DNO's and customer's systems will differ - the lower Ra the less the customer sees and the more the DNO's system (including N/CNE) will be affected.
To be honest I can't see it being worse than the original PME system for a CNE break near the substation where the DNO's electrode was a few tens of metres of copper buried within the substation compound while the consumers side was connected to literally miles of metallic gas and water pipes.
- Andy.
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site